The overall goal of this project is to understand the cellular mechanisms used by neuromodulators to control behavioural plasticity. Specifically, we are using multiphoton microscopy and electrophysiology to study the cellular mechanisms by which neuromodulators produce various motor patterns in a small, well characterized, neural network-- the lobster stomatogastric ganglion. Neuromodulators such as dopamine and serotonin play central roles in the regulation of behavior in both vertebrates and invertebrates. The Harris-Warrick group has analyzed the effects of dopamine, serotonin and octopamine on the well-studied 14-cell pyloric network in the crustacean stomatogastric ganglion (STG). These compounds are endogenous neuromodulators of the pyloric network and when bath-applied to the stomatogastric ganglion, each amine evokes a unique variant on the rhythmic motor pattern generated by the pyloric network, with changes in the cycle frequency, active neurons, phasing and intensity of n euronal firing. We are currently using multiphoton microscopy measure of calcium signals and monitor the time course and spatial distribution of the calcium changes in STG neurons elicited by amines. These experiments are designed to answer two major questions: (1) do amines modify calcium entry and/or release from intracellular stores, and (2) are the actions of amines on calcium activity different at nerve terminals (where they might affect transmitter release) than in other regions of the cell where calcium might modulate the intrinsic firing properties of the cell?